Braze alloy compositions and brazing methods for superalloys

ABSTRACT

A multi-component braze filler alloy comprising at least 70% by weight MarM509A superalloy with the remainder MarM509B superalloy is diffusion brazed to a CM247 alloy base substrate, such as a gas turbine blade or vane. It is shown that generally higher braze temperatures lead to improved results including the possibility of re-welding such a brazed component, resulting in a re-repaired brazed component capable of continued commercial service.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. patent application Ser. No.14/070,626 filed on Nov. 4, 2013, the disclosure of which is herebyincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the brazing and repair of superalloycomponents, and in particular to brazing compositions and methods forbrazing superalloy blade and vane components used in gas turbines, withbraze compositions and brazing procedures that consistently provide goodbrazing of test samples, some embodiments of which permit post brazewelding without substantial degradation of structural properties.

2. Description of the Prior Art

Structural repair or new fabrication of nickel and cobalt basedsuperalloy materials that are used to manufacture turbine components,such as cast turbine blades, are challenging, due in part to themetallurgic properties of the superalloy material. For example, asuperalloy having more than about 6% aggregate aluminum or titaniumcontent, such as nickel-base superalloys with low carbon content e.g.,CM247, is typically more susceptible to solidification cracking whensubjected to high-temperature welding than a lower aluminum-titaniumcontent superalloy, e.g., X-750. Superalloys used in finished turbineblades are typically strengthened during post casting heat treatments,which render them difficult materials upon which to perform subsequentstructural welding repairs. Currently used welding processes forsuperalloy fabrication or repair generally involve substantial meltingof the substrate adjoining the weld preparation, and complete melting ofthe added welding filler material. When a blade constructed of such amaterial is welded with filler of the same or similar alloy, e.g., forstructural repair, the blade is susceptible to solidification cracking(aka liquation cracking) within and proximate to the weld. Post weldsolidification cracked superalloy vanes and blades are generallyscrapped as unrepairable, after considerable time and expense wasalready expended to attempt to repair the blade. Given the shortcomingsof superalloy structural repair welding, often the only commerciallyacceptable solution is to scrap damaged turbine blades that requirestructural repair, because past experience has shown limited success ofsuch structural repairs. Thus repairs have been limited to thoseparticular materials, components and types of structural damage thathave in the past been proven amenable to successful repair by cosmeticwelding, employing more ductile welding filler materials with reducedstructural strength. Blades needing welded structural repairs with aknown relatively high risk of post weld solidification cracking aregenerally scrapped. Providing brazing compositions and methods that canwithstand post braze welding without significant solidification crackingor other degradation of structural, mechanical or other properties wouldpermit repair and reuse of such components, an important economicbenefit.

Non-structural repair or fabrication of metal components, includingsuperalloy components, typically involves replacing damaged material (orjoining two components of newly fabricated material) with mismatchedalloy material of lesser structural properties, where the superiorstructural performance of the original substrate material is not neededin the localized region. For example, such non-structural or “cosmetic”repair may be used in order to restore the repaired component's originalprofile geometry. For the repair of gas turbine components, an exampleof cosmetic repair is the filling of surface pits, cracks or other voidson a turbine blade airfoil in order to restore its original aerodynamicprofile, for cases in which the mechanical properties of the blade'slocalized exterior surface are not critical for the structural integrityof the entire blade. Cosmetic repair or fabrication is often achieved byusing oxidation resistant weld or braze alloys of lower strength thanthe blade body superalloy substrate, but having higher ductility andemploying a lower application temperature that does not degrade thestructural or material properties of the superalloy substrate.

Diffusion brazing has been utilized to join superalloy components forrepair or fabrication by interposing brazing alloy between theirabutting surfaces to be joined, and heating those components in afurnace (often isolated from ambient air under vacuum or within an inertatmosphere) until the brazing alloy liquefies and diffuses within thesubstrates of the to-be-conjoined components. Diffusion brazing can alsobe used to fill surface defects, such as localized surface and/ornon-structural cracks, in superalloy components by inserting brazingalloy into the defect and heating the component in a furnace to liquefythe brazing alloy and thus fill the crack. In some types of repairs atorch rather than a furnace can be used as a localized heat source tomelt the brazing alloy. Braze repaired superalloy blades and vanes aretypically returned to service.

In a subsequent gas turbine inspection cycle, blades or vanes that areidentified as having defects in previously braze-repaired surfaces riskremelt and migration of old braze material if the component were againheated for repairs. Often for commercial cost saving reasons blades withdefects in previously brazed portions are scrapped rather than riskpotential repair failure attributable to remelt migration of old brazematerial.

Braze material with the commercial designation Mar-M-509 ® (A registeredtrademark of Martin Marietta Co. and commercially available, forexample, from Praxair Surface Technologies, Inc. Indianapolis, Ind.under their designations CO-222, CO-333) is a high chrome contentsuperalloy braze material that has commonly been used for repair ofCM247 alloy turbine blade and vane components. Products with similarperformance characteristics are also commercially available from SulzerMetco as Amdry MM509 and Amdry MM509B. However, it would be desirable toutilize a braze material including CM247, so that the braze material andthe component substrate have more closely matched material properties. Acommercial designation for CM247 is MAR-M-247, one form of which isavailable from Praxair Surface Technologies under their designationNI-335-5.

Thus, a need exists in the art for a braze composition having materialproperties more closely matching those of CM247 superalloy components,such as gas turbine blades and vanes, that can be rewelded without meltmigration from the weld zone and that resists solidification cracking atthe weld interface or surrounding areas.

SUMMARY OF THE INVENTION

Some embodiments of the present invention relate to braze alloycompositions comprising a range of approximately 60%-70% by weight ofCM247 base alloy and the balance of MarM509A/MarM509B braze alloy. Whenapplied to a CM247 alloy substrate component by diffusion brazing, suchcompositions do not significantly demelt and migrate when rewelded in asubsequent weld repair. Even after performing a post weld solution cyclethe braze material resists solidification cracks at the weld interfaceand surrounding areas.

It is also demonstrated herein that different braze processing canimprove the performance of MarM509A/MarM509B braze alloy mixtures overthat typically experienced in prior art brazing using these materials.

Thus, the present invention includes compositions of matter and brazeprocesses suitable for improved brazing of superalloy componentswherein, pursuant to some embodiments of the invention, the brazedregions are capable of post braze welding repair without substantialsolidification carcking, and also includes superalloy components sobrazed and subsequently repaired by welding.

The features of the present invention may be applied jointly orseverally in any combination or sub-combination by those skilled in theart.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1: Tabular enumeration of some braze tests performed pursuant tosome embodiments of the present invention;

FIG. 2: Typical vacuum cleaning furnace cycle pursuant to someembodiments of the present invention;

FIG. 3: Photomicrograph of typical cracks created for braze tests;

FIG. 4: Photomicrograph of typical cracks created for braze testsfollowing the introduction of paste into the cracks by regulatedcompressed air behind a piston forcing the paste through an applicationneedle, which was used to work the paste into the cracks as required.The paste comprises a liquid binder mixed with a braze alloy;

FIG. 5: Braze cycle used for some of the braze tests conducted herein,representing a typical braze cycle with multiple stop points in the rampup to braze temperature, a short dwell at braze temperature and then adrop in temperature, and hold for alloy diffusion;

FIG. 6: Photomicrograph after completion of braze furnace cycle for the50/50 alloy mix MarM509A/B;

FIG. 7: Photomicrograph after completion of braze furnace cycle for the60/40 alloy mix MarM509A/B;

FIG. 8: Photomicrograph after completion of braze furnace cycle for the70/30 alloy mix MarM509A/B;

FIG. 9: Photomicrograph at 50× after completion of braze furnace cyclefor the 50/50 alloy mix MarM509A/B (etched);

FIG. 10: Photomicrograph at 50× after completion of braze furnace cyclefor the 60/40 alloy mix MarM509A/B;

FIG. 11: Photomicrograph at 50× after completion of braze furnace cyclefor the 70/30 alloy mix MarM509A/B (etched);

FIG. 12: Remelt Evaluation. Photomicrograph following a solution heattreat cycle after completion of the braze furnace cycle to evaluate theaffect on the braze of possible normal repair processes followingbrazing. Three mixtures of MarM/A/B are depicted (left to right), 70/30,60/40, 50/50;

FIG. 13: Tabular enumeration of some braze tests performed pursuant tosome embodiments of the present invention;

FIG. 14: Photomicrograph of cracks created in samples for braze test;

FIG. 15: Photomicrograph of cracks created in samples for braze testprior to HF cleaning;

FIG. 16: Photomicrograph of cracks created in samples for braze testfollowing FIC cleaning and brazing;

FIG. 17: Alloy Application. Photomicrograph of typical cracks createdfor braze tests following the introduction of paste into the cracks byregulated compressed air behind a piston forcing the paste through anapplication needle, which was used to work the paste into the cracks asrequired. The paste comprises a liquid binder mixed with a braze alloy;

FIG. 18: Typical braze cycle as employed for some embodiments herein;

FIG. 19: Photomicrograph after completion of braze furnace cycle for the60/40 alloy mix MarM509A/B;

FIG. 20: Photomicrograph after completion of braze furnace cycle for the70/30 alloy mix MarM509A/B;

FIG. 21: Photomicrograph after completion of braze furnace cycle for the80/20 alloy mix MarM509A/B;

FIG. 22: Photomicrograph after completion of braze furnace cycle for the60/40 alloy mix CM247/BRB;

FIG. 23: Photomicrograph after completion of braze furnace cycle for the70/30 alloy mix CM247/BRB;

FIG. 24: Photomicrograph after completion of braze furnace cycle for the80/20 alloy mix CM247/BRB;

FIG. 25: Photomicrograph at 50× after completion of braze furnace cyclefor the 60/40 alloy mix MarM509A/B;

FIG. 26: Photomicrograph at 50× after completion of braze furnace cyclefor the 70/30 alloy mix MarM509A/B;

FIG. 27: Photomicrograph at 50× after completion of braze furnace cyclefor the 80/20 alloy mix MarM509A/B;

FIG. 28: Photomicrograph at 50× after completion of braze furnace cyclefor the 60/40 alloy mix CM247/BRB;

FIG. 29: Photomicrograph at 50× after completion of braze furnace cyclefor the 70/30 alloy mix CM247/BRB;

FIG. 30: Photomicrograph at 50× after completion of braze furnace cyclefor the 80/20 alloy mix CM247/BRB;

FIG. 31: Perspective and cross sectional photomicrograph following asolution heat treat cycle (2250 deg. F.) after completion of the brazefurnace cycle to evaluate the affect on the braze of possible normalrepair processes following brazing of CM247/BRB on a CM247 substratewith IN625 filler material;

FIG. 32: Photomicrograph following a solution heat treat cycle (2250deg. F.) after completion of the braze furnace cycle to evaluate theaffect on the braze of possible normal repair processes followingbrazing of MarM509/A/B on a CM247 substrate with IN625 filler material.In the drawings and in the specification, “MarM509 or “509” is anabbreviation of MarM509A or 509A respectively; and

FIG. 33: Results of mechanical testing for various braze materials andmixtures.

DETAILED DESCRIPTION

Improved high temperature repair braze compositions and methods aredescribed, some embodiments of which achieve compositions, mechanicaland structural properties nearer to that of the base metal. In someembodiments, the brazed region is subsequently weldable withoutincurring serious degradation of properties. After considering thefollowing detailed description, those skilled in the art will clearlyrealize that the teachings of the present invention can be readilyutilized in a multi-component braze filler alloy comprising variouscompositions of CM247 alloy, MarM509A, MarM509B and BRB braze alloy thatare suitable for diffusion brazing to a nickel-based superalloysubstrate such as CM247, such as typically used in a gas turbine bladeor vane. The substrate/braze interface pursuant to some embodiments ofthe present invention is shown to be amenable to subsequent weldingrepair without incurring damaging demelting and/or migration of thebraze alloy from the interface region. The weld zone and surroundingarea are resistant to solidification cracking After the alloycomposition is brazed to the base substrate the component may bereturned to service. Thereafter, the component remains repairable bywelding, if needed to correct future in-service defects, rather thanscraping the component, with the weld-repaired component having reducedrisk of solidification cracking as a consequence of the weldingoperation. This represents an important improvement over conventionalbrazing compositions and methods in which post braze welding typicallydegrades structural properties to such an extent that the component isno longer suitable for normal use.

CM247

Alloy 247 is an exemplary material for the fabrication of gas turbinecomponents, and thus, to be concrete in our descriptions, specificformulations and procedures for the repair of alloy 247 components aredescribed herein. However, the compositions and procedures describedherein are not inherently limited to alloy 247, but can beadvantageously used for the repair of other superalloys as apparent tothose having ordinary skills in the art of superalloy material scienceand superalloy component repair.

The following composition has been found to be among those advantageousas a braze filler alloy for use with alloy 247, and comprisesapproximately 60%-70% by weight CM247 alloy with the remainder being BRBbraze alloy. All percents are weight percents and are intended to beapproximate, in which slight deviations about the quoted values are notexpected to cause dramatic changes in performance or properties. A moreprecise range of applicability can readily be determined by routineexperimentation.

CM 247 has a typical composition as follows (from Huang and Koo, Mat.Transactions, 45, 562-568 (2004), the entire contents of which isincorporated herein by reference for all purposes.):Ni(X_(Ni))—C(X_(C))—Cr(X_(Cr))—Co(X_(Co))—Al(X_(Al))—B(X_(B))—W(X_(W))—Mo(X_(Mo))—Ta(X_(Ta))—Ti(X_(Ti))—Hf(X_(Hf))—Zr(X_(Zr)).in which the weight percentages X_(z) are approximately as follows forCM247 alloy in Eq. 1.

C: X_(C)=0.07%

Cr: X_(Cr)=8.1%

Co: X_(Co)=9.2%

Al: X_(Al)=5.6%

B: X_(B)=0.015%

W: X_(W)=9.5%

Mo: X_(Mo)=0.5%

Ta: X_(Ta)=3.2%

Ti: X_(Ti)=0.7%

Hf: X_(Hf)=1.4%

Zr: X_(Zr)=0.015%

Ni: X_(Ni)=(balance)  Eq. 1.

Slight variations in these proportions are within normal commercialusage. For example, the commercial CM247 known as MAR-M-247 has thecomposition given in Eq. 2 as provided by the vendor.

C: X_(C)=0.15%

Cr: X_(Cr)=8.4%

Co: X_(Co)=10.0%

Al: X_(Al)=5.5%

B: X_(B)=0.015%

W: X_(W)=10.0%

Mo: X_(Mo)=0.7%

Ta: X_(Ta)=3.0%

Ti: X_(Ti)=1.0%

Hf: X_(Hf)=1.5%

Zr: X_(Zr)=0.05%

Ni: X_(Ni)=(balance)

Thus, in view of this data, we use CM 247 herein to denote a superalloyhaving a composition in approximately the following ranges as given inEq. 3.

CM 247

C: X_(C)=0.07-0.15%

Cr: X_(Cr)=8.1-8.4%

Co: X_(Co)=9.2-10.0%

Al: X_(Al)=5.5-5.6%

B: X_(B)=0.015%

W: X_(W)=9.5-10.0%

Mo: X_(Mo)=0.5-0.7%

Ta: X_(Ta)=3.0-3.2%

Ti: X_(Ti)=0.7-1.0%

Hf: X_(Hf)=1.4-1.5%

Zr: X_(Zr)=0.015-0.05%

Ni: X_(Ni)=(balance)  Eq. 3.

The results reported herein employ AIMRO CM 247, substantially the sameas CM247 described herein. For economy of language, we use “CM247”herein to denote a material having a composition substantially withinthe ranges given by Eq. 3.

The experimental data obtained herein relates to directionallysolidified CM 247 (CM247DS). However, it is not expected that the use ofsingle crystal, polycrystalline or other forms of CM 247 will have asignificant effect on the results.

BRB

BRB is a nickel-based diffusion braze alloy, such as commerciallyavailable through Sulzer Metco as Amdry BRB. The BRB material usedherein has substantially the following composition:Ni(X_(Ni))—Cr(X_(Cr))—Co(X_(Co))—Al(X_(Al))—B(X_(B)) in which the weightpercentages X_(z) are approximately in the following ranges:

BRB

Cr: X_(Cr)=13.0-14.0%

Co: X_(Co)=9.0-10.0%

Al: X_(Al)=3.5-4.5%

B: X_(B)=2.25-2.75%

Ni: X_(Ni)=(balance)  Eq. 4.

with a particle size distribution having a nominal range −150+45 μm(micrometers), mesh (ASTM) −100+325 mesh. For economy of language, weuse “BRB” herein to denote a material having a composition substantiallywithin the ranges given by Eq. 4.

MarM509A/MarM509B

Brazing tests and improved brazing results are also described herein forcobalt based superalloys containing relatively large amounts of chromiumand nickel commercially known under the trade names MarM509 (MarM509A,or briefly “509A”), MarM509B (“509B”). The particular MarM509A/Bmaterials used herein were obtained from Sulzer Metco under the tradenames Amdry MM509 (509A) and Amdry MM509B (509B). The compositionsprovided by the vendor are as follows:

509A (Eq. 5A) 509B (Eq. 5B) C: X_(C) = 0.6% C: X_(C) = 0.6% Cr: X_(Cr) =24% Cr: X_(Cr) = 23% Ni: X_(Ni) = 10% Ni: X_(Ni) = 10% W: X_(W) = 7% W:X_(W) = 7% Ta: X_(Ta) = 3.5% Ta: X_(Ta) = 3.5% Co: X_(Co) = (balance) B:X_(B) = 2.5% Co: X_(Co) = (balance)

Studies were carried out using several of the present braze compositionalloys pursuant to some embodiments of the present invention to repaircracks on an alloy 247 blade substrates and subsequently weld the brazedblades with the results described herein. It is apparent that theseresults demonstrate an improvement over prior art brazing compositionsand methods, leading towards more effective, less expensive,service-ready repairs of superalloy components following brazing.

Results: CM247 DS Base Material Braze with CM247/BRB andMarM509A/MarM509B.

Improvements obtainable pursuant to some embodiments of the presentinvention, employing different mixtures of CM247/BRB andMarM509A/MarM509B under different processing conditions are presented.To be concrete in our discussion, we consider brazing a CM247 substratematerial, more particularly, a component comprising service run row 1turbine blades from the W501G engine made of CM247 DS castings. Theseexamples are intended to be illustrative, not limiting, as one skilledin the art can readily adapt these compositions and methods to othersubstrate materials and/or components without undue experimentation.That is, these tests are typical examples of results obtainable and donot limit the scope of the present invention to specific compositions orprocess conditions disclosed. However, this particular example ofturbine blades has considerable practical and commercial importance initself.

The tests described herein were conducted in separate rounds consistingof different braze base alloys of multiple mixtures with one brazealloy, different braze furnace cycles and different substratepreparation methods.

Several criteria were used to evaluate the results of these tests:

-   -   1. General visual appearance of the braze.    -   2. Metallographic evaluation of the interface, crack fill and        porosity.    -   3. Remelt of the braze during a post braze solution heat treat        cycle.    -   4. Post braze weldability.    -   5. Mechanical testing including surface hardness, UTS (ultimate        tensile strength), yield and elongation.

Examples A: MarM509A/MarM509B (“MarM509A/B”) Mixtures

“MarM509A/B” denotes a mixture of 509A and 509B materials having thecompositions substantially as given in Eqs. 5A and 5B respectively.

Example A.I: Surface Preparation

Two methods of surface preparation were combined for this test. Amechanical cleaning of the area was performed, using carbide blend toolsto create a simulated crack approximately 0.050″ (inches) in width byapproximately 0.050″ in depth. A typical example is shown in FIG. 3.Following the mechanical cleaning and the creation of the simulatedcracks, the blade material was subjected to a vacuum cleaning furnacecycle according to the procedures given in FIG. 2.

Example A.II: Alloy Application

Three different mixtures of a single base and a single braze alloy weretested. In all of these cases, the braze alloy was MarM509B (“509B”) andthe base was MarM509A (“509A”). The base was mixed with braze alloy withweight ratios 509A/509B of 50/50, 60/40, 70/30 and then combined withliquid binder in the amount of about 10%-15% by volume to form a paste.The paste was then worked into a plastic cartridge with regulatedcompressed air behind a piston to force the paste through an applicationneedle that was used to work the paste into the cracks as required. Stopoff can be applied as required to the base material around the braze toassure that the alloy does not run outside the intended repair zone. Atypical result of this alloy-application, crack-filling step is shown inFIG. 4.

Example A-III: Braze Cycle

The braze cycle employed in this Example A represents a typical brazecycle with multiple stop points in the ramp up to braze temperature, adwell at braze temperature followed by a drop in temperature and aholding period for alloy diffusion. A typical cycle is given in FIG. 5.It is important to note that 2200 deg. F. is the highest temperatureapplied during all braze cycles employed in these Examples-A forMarM509A/B.

Example A-IV: Results

Results from seven tests are reported herein, identified as Example A-04to Example A-10 in FIG. 1.

A-IV(i): Post Braze Visual Evaluation.

A visual inspection was performed after the braze furnace cycle wascompleted. The results for MarM509A/B (Examples A-04, A-05, A-06 ofFIG. 1) are shown as follows:

FIG. 6 is a photomicrograph of results obtained with the 50/50 alloymixture. This 50/50 alloy mixture appears hot (that is, close to orexceeding its melting point) and perhaps has a slight undercut aroundthe braze edges, although this cannot be definitively determined fromthis micrograph.

FIG. 7 is a photomicrograph of results obtained with the 60/40 alloymixture. This 60/40 alloy mixture appears to have a reasonably smoothappearance and apparently shows continuous flow at the edges.

FIG. 8 is a photomicrograph of results obtained with the 70/30 alloymixture. This 70/30 alloy mixture apparently shows a sluggish flowresulting in a significant transition at the braze edges.

A-IV(ii): Metallographic Evaluation

Metallographic evaluation was performed at 50× for flow, interfacequality, porosity and other defects. The results for MarM509A/B(Examples A-04, A-05, A-06 of FIG. 1) are shown as follows:

FIG. 9 is the metallographic result for the 50/50 braze mixture. Thisphotomicrograph apparently indicates good flow into the base material,providing a smooth transition from the braze repair area. The interfaceappears to be substantially acceptable but with a hint of being hot.Porosity was below 1% of the measured area of the repair.

FIG. 10 is the metallographic result for the 60/40 braze mixture. Thisphotomicrograph apparently indicates good flow into the base material,providing a smooth transition from the braze repair area. The interfaceappears to be excellent and porosity was below 1% of the measured areaof the repair.

FIG. 11 is the metallographic result for the 70/30 braze mixture. Thisphotomicrograph apparently indicates sluggish flow into the basematerial with a sharp contrast from the blaze alloy. The interfaceappears to be substantially acceptable but the porosity was rather highwith severe voiding arising from a lack of adequate alloy flow.

A-IV(iii): Remelt Evaluation

The three different mixtures considered in this Example-A, MarM509A/B(Examples-04, -05, -06 of FIG. 1) were subjected to a typical solutionheat treat cycle after the braze was completed in order to determine ifthe braze alloy would likely be affected if the component so brazed werelater subjected to a normal repair process. The remelt percentage wascalculated by comparing the alloy height following solution heattreatment to the alloy height following the braze process but before thesolution heat treatment. For 50/50 (MarM509A/B) more than 100% remeltwas observed. The alloy returned to its liquid state and ran off theworkpiece resulting in a depression below the level of the originalsurface. For 60/40 (MarM509A/B), approximately 50% alloy height loss wasobserved. For 70/30 (MarM509A/B), approximately 30% alloy height losswas observed. A photomicrograph of these results is provided in FIG. 12.

A-IV(iv): Post Braze Weld Evaluation

No weld evaluation was performed on these braze samples due to thefailure of the remelt tests.

A-IV(v): Mechanical Testing

No mechanical testing was performed on these samples due to the failureof the remelt tests.

Example B: CM247/BRB Mixtures

“CM247/BRB” denotes a mixture of CM247 and BRB materials having thecompositions substantially as given in Eqs. 3 and 4 respectively.

Additional braze tests were performed combining braze and diffusioncycles performed to the same times and temperature as used for the basematerial heat treat cycle. The tests consisted of one braze cycle, onesurface preparation method, with two base alloys mixed using threedifferent levels of two different braze alloys.

Example B-I: Surface Preparation

The braze surfaces were prepared using a mechanical cleaning method withcarbide blend tools to create a simulated crack approximately 0.050″ inwidth by approximately 0.050″ in depth. No vacuum cleaning furnace cyclewas performed after the mechanical cleaning operation. One blade wascleaned using a fluoride ion cleaning (FIC) furnace with HF gas toprepare the surface for braze. FIGS. 14, 15, 16 show typical blades atvarious stages in the surface preparation process.

Example B-II: Alloy Application

Three different mixtures of two base and braze alloys were prepared andtested: (MarM-509A base/MarM-509B braze) and (CM247/BRB).

The MarM-509A (“509A”) base was mixed with MarM-509B (“509B”) brazealloy in the ratios (by weight) 60/40, 70/30, 80/20 (509A/509B). Thesemixtures were then combined with liquid binder in an amount of 10%-15%by volume to form a paste. The CM247 base was mixed with BRB braze alloyin the ratios CM247/BRB (by weight) 60/40, 70/30, 80/20. These mixtureswere then combined with liquid binder in an amount of 10%-15% by volumeto form a paste. Thus, six pastes were prepared and tested.

Each paste was worked into a plastic cartridge with regulated compressedair behind a piston to force the paste through an application needlethat was used to work the paste into the cracks as required. Stop offcan be applied as required to the base material around the braze toassure that the alloy does not run outside the intended repair zone.FIG. 17 shows typical blades following the step of alloy application.

Example B-III: Braze Cycle

The braze cycle used was chosen to have the same times and temperaturesas a standard solution heat treat cycle, as given in FIG. 18.

Example B-1V: Results

Results from 20 tests are reported herein, identified as Example B-14 toExample B-39 in FIG. 13.

B-IV(i): Post Braze Visual Evaluation

A visual inspection was performed following the combined braze anddiffusion furnace cycle of FIG. 18. The results for MarM509A/B (ExamplesB-29, B-30, B-31) are shown as follows:

FIG. 19 is a photomicrograph of results obtained with the 60/40 alloymixture. This mixture appears hot with excessive run of the alloy fromthe braze area.

FIG. 20 is a photomicrograph of results obtained with the 70/30 alloymixture. This mixture has an excellent smooth appearance with goodcontinuous flow at the edges.

FIG. 21 is a photomicrograph of results obtained with the 80/20 alloymixture. This mixture has a slight sluggish appearance but appears to beacceptable with some contrast at the braze edges.

The results of the visual inspection for CM247/BRB (Examples B-14, B-15,B-16) are shown as follows:

FIG. 22 is a photomicrograph of results obtained with the 60/40 alloymixture. This mixture appears very hot with excessive run of the alloyfrom the braze area.

FIG. 23 is a photomicrograph of results obtained with the 70/30 alloymixture. This mixture has a good smooth appearance at the edges withsome alloy flow from the repair area.

FIG. 24 is a photomicrograph of results obtained with the 80/20 alloymixture. This mixture has a smooth appearance at the braze edges with aslight sluggish appearance, but probably an acceptable appearance.

B-IV(ii): Metallographic Evaluation

Metallographic evaluation was performed at 50× for flow, interfacequality, porosity and other defects. The results for MarM509A/B(Examples B-29, B-30, B-31) are shown as follows:

FIG. 25 is a photomicrograph of results obtained with the 60/40 brazemixture. The photomicrograph apparently shows good flow into the basematerial providing a smooth transition from the braze alloy. Theinterface appears to be acceptable but with a hint of being hot.Porosity was similar to the casting material and below about 1% of themeasured volume of the repair area.

FIG. 26 is a photomicrograph of results obtained with the 70/30 brazemixture. The photomicrograph shows excellent flow into the basematerial, providing a smooth transition from the edges. The interface isexcellent. The porosity is similar to the casting material and belowabout 1% of the measured volume of the repaired area. The right edge ofthe braze was apparently missed and not filled during the application ofthe alloy.

FIG. 27 is a photomicrograph of results obtained with the 80/20 brazealloy mixture. The photomicrograph shows sluggish flow into the basematerial with a sharp contrast from the regions at the edges. The actualinterface is apparently acceptable but the porosity was beyond typicallyacceptable limits with severe voiding from lack of flow.

The results for CM247/BRB (Examples B-14, B-15, B-16) are shown asfollows:

FIG. 28 is a photomicrograph of results obtained with the 60/40 brazemixture. The photomicrograph apparently shows good flow into the basematerial providing a smooth transition from the braze repair area. Theinterface appears to be acceptable but with a hint of being hot.Porosity was similar to the casting material and below about 1% of themeasured volume of the repair area.

FIG. 29 is a photomicrograph of results obtained with the 70/30 brazemixture. The photomicrograph shows excellent flow into the basematerial, providing a smooth transition from the braze repair area. Theinterface is excellent. The porosity is similar to the casting materialand below about 1% of the measured volume of the repair area.

FIG. 30 is a photomicrograph of results obtained with the 80/20 brazealloy mixture. The photomicrograph shows sluggish flow into the basematerial with a sharp contrast at the edges. The actual interface isapparently acceptable but the porosity was beyond typically acceptablelimits with severe voiding from lack of flow.

Example B-IV(iii): Remelt Evaluation

Three different mixtures of MarM509/A/B were subjected to a solutionheat treat cycle (2270 deg. F.) after the initial braze was completed todetermine if the braze would be affected during a future normal repairprocess. The remelt percentage was calculated by comparing the beadheight following the solution heat treat cycle with the post braze alloybead height.

60/40 Remelt Evaluation: 100% of the alloy height loss was observed(Total Remelt).

70/30 Remelt Evaluation: An alloy height loss of approximately 10% ofwas observed.

80/20 Remelt Evaluation: No alloy height loss was observed.

It is important to note that this remelt evaluation shows markedimprovement over the remelt discussed in Example A-IV(iii) for the 70/30and 80/20 compositions. We attribute this to the use of generally higherbraze temperature and times for these Examples-B in comparison to thebraze temperature and times used in Example-A. From FIG. 18 we see thatExample-B components were held at 2270 deg. F. (±12 deg. F.) for 240-255min. while in Example-A, the components were held at 2200 deg. F. (±10deg. F.) for 40 min. and at 2050 deg. F. (±10 deg. F.) for 270 min.(FIG. 5). Thus, we conclude that the different time-temperature protocolhas an important effect on the properties of braze joints for 509A/509Bbraze compositions and that ratios of 509A/509B less than about 70/30are contraindicated.

Three different mixtures of CM247/BRB were subjected to a solution heattreat cycle (2270 deg. F.) after the initial braze was completed todetermine if the braze would be affected during a future normal repairprocess. The remelt percentage was calculated by comparing the beadheight following the solution heat treat cycle with the post braze alloybead height.

60/40 Remelt Evaluation: 100% of the alloy height loss was observed(Total Remelt).

70/30 Remelt Evaluation: An alloy height loss of approximately 10% ofwas observed.

80/20 Remelt Evaluation: No alloy height loss was observed.

In summary, 60/40 shows good flowability, deposition and mechanicalproperties, but lacks good remelt characteristics when compared to 70/30or 80/20. It appears advantageous to use the 70/30 mixture if the brazecomposition is to be applied and if it is to be subjected to anyre-heating above about 2270 deg.

Example B-IV(iv): Post Braze Weld Evaluation

An evaluation was done on CM247/BRB (Example B-24) to observe the effectof a post braze weld repair using IN625 filler material. The test wascompleted after a post weld solution cycle. However, no age heat treatwas performed. No cracks were observed at the interface or surroundingareas, and the welder performing the work reported that this weld seemedto be similar to that of a weld of the base alloy. See FIG. 31.

An evaluation was done on MarM509/A/B (Example B-39) to observe theeffect of a post braze weld repair using IN625 filler material. The testwas completed after a post weld solution cycle. However, no age heattreat was performed. No cracks were observed at the interface orsurrounding areas, and the welder performing the work reported that thisweld seemed to be similar to that of a weld of the base alloy. See FIG.32. Therefore, the 70/30 mixture is considered to be advantageous on thebasis of the following tests and/or observations:

Flowability (ability to fill the gaps and cracks)

Remelt

Reweld

Hardness

Tensile Tests

Mechanical Tests

Example B-IV(vi): Mechanical Testing

Mechanical testing was done to compare the hardness, tensile strength,yield and elongation of the two alloys of various mixtures against thebase material and the base material with IN625 weld repairs. The testswere carried out by Metcut Research, Inc. of Cincinnati, Ohio accordingto the procedures given in FIG. 33. Six samples of each type were testedand the average of those six are reported in FIG. 33 including the BaseMaterial (Specimen 45) and the base material with IN625 weld repairs(Specimen 46).

CONCLUSIONS Surface Preparation

Mechanical cleaning provided an excellent braze surface and interfacebetween braze and the base alloy. The mechanical-vacuum cleaning processused in Example A provided an equal interface, however no better thanthe mechanical cleaning process alone. No apparent benefits resultedfrom using the extra furnace cycle. Examples B were performed aftermechanical preparation of the surface using a carbide burr to remove thetop layer of material. The mechanical test samples were also preparedusing this same method which further indicates the acceptability of theprocess. The FIC cleaning process did provide a better visual wetting ofthe alloy and apparently a very slightly improved interface observedduring the lab examination. However, all mechanical tests performedshowed a consistent loss of tensile strength of about 4%-5%.

Braze Alloy Selection and Application.

The CM247 base alloy mixed with BRB braze material consistently providedthe best test results observed herein. The CM247 and MarM509A base alloypowders provided substantially equal results with regard to visual flowand interface quality. However, when mixed with equal amounts of brazealloy the CM247 typically was slightly more free flowing. The CM247alloy typically provided 13%-15% better tensile strength values than theMarM509 alloy of the same mixture with higher and more consistent strainrate through 2.0% yield values. Both CM247 and MarM509 braze providedsubstantially equal visual results when welded with IN625 fillermaterial. However, it is generally better practice to strive to have thechemical composition of the repair area as close to the original basematerial as possible (that is, a higher base alloy content in themixtures).

The 70/30 mixture of the CM247 base powder with the BRB braze alloyprovided better results with regard to porosity, crack fill, post brazesolution cycle remelt and tensile strength. It is also observed that thebraze elongation with the CM247 base alloy was typically superior to theMarM509 alloy. However the elongation numbers typically decreased fromthe 60/40 mixture up to the 70/30 mixture.

The remelt evaluation with the 70/30 mixture seemed to be acceptablewith regard to future repair cycles with only a slight hint (10% heightloss) of the alloy turning liquid during subsequent solution cycles.

Braze Cycle

All braze cycles performed with the lower braze cycle temperature (2200deg. F.) experienced complete remelt test failures even when higher basematerial alloy was added to the mixture. The higher braze cycletemperature used in the second (B) tests provided improved results inthe remelt evaluations.

The advantage to the higher temperature braze cycle, which in effect isequal to the standard solution heat treat cycle of the base material, isthat the opportunity to braze before or after weld repairs is alwayspresent without the addition of heat treat cycles which add cost to therepair process and may have some unknown effect to the base materialproperties.

Although various embodiments that incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings. The invention is not limited in itsapplication to the exemplary embodiment details of construction and thearrangement of components set forth in the description or illustrated inthe drawings. The invention is capable of other embodiments and of beingpracticed or of being carried out in various ways. Also, it is to beunderstood that the phraseology and terminology used herein is for thepurpose of description and should not be regarded as limiting. The useof “including,” “comprising,” or “having” and variations thereof hereinis meant to encompass the items listed thereafter and equivalentsthereof as well as additional items.

We claim:
 1. A material for the braze repair of a nickel-base superalloyturbine component comprising: a MarM509A/B mixture of no less thanapproximately 70% by weight of MarM509A base alloy and the balancecomprising MarM509B braze alloy, including about 10%-15% by volume of aliquid binder to form a paste.
 2. A material as in claim 1 wherein thenickel-base superalloy turbine component comprises CM247.
 3. A materialas in claim 1, wherein the nickel-base superalloy component is a turbinevane or blade.
 4. An article of manufacture comprising a Ni-basesuperalloy component wherein the Ni-base superalloy component has aportion thereof repaired by brazing with a brazing material according toclaim
 1. 5. An article of manufacture as in claim 4, wherein the Ni-basesuperalloy turbine component comprises CM247.
 6. An article ofmanufacture as in claim 4, wherein the Ni-base superalloy component is aturbine vane or blade.
 7. An article of manufacture as in claim 4,wherein the Ni-base superalloy component has a portion thereofre-repaired by post braze welding and is suitable for continued service.8. An article of manufacture as in claim 7, wherein the Ni-basesuperalloy turbine component comprises CM247.
 9. An article ofmanufacture as in claim 7, wherein the Ni-base superalloy component is aturbine vane or blade.
 10. An article of manufacture as in claim 4,wherein the Ni-base superalloy component is post-braze heat treated andis suitable for continued service.
 11. An article of manufacture as inclaim 10, wherein the Ni-base superalloy turbine component comprisesCM247 or is a turbine blade or is a turbine vane.